As the barrenwort deriving from plants belonging to the genus Epimedium, there are known Epimedium macranthum, M. et. D. var. violaceum, Fr., Epimedium sagittatum, Bak., Epimedium macranthum, M. et. D., Epimedium koreanum, Nak., etc. These plants are perennial herbs growing naturally in Japan, China and Korea, etc. The barrenwort is a crude drug obtained from a single species or a mixture of two or more of species belonging to the genus Epimedium by cutting down the plants at roots in June or July and drying them in the shade under good ventilation while keeping out rain and dew. The plants belonging to the genus Epimedium are perennials belonging to the family Berberidaceae, having the height of 30 to 60 cm and growing wild in fields and mountains in Japan, China, Korea or the like. The barrenwort marketed in Japan and Korea derives from Epimedium macranthum, M. et D. var. violaceum, Fr. or Epimedium koreanum Nak.; the barrenwort marketed in China, from Epimedium sagittatum Bak. or Epimedium koreanum Nak. In the field of Chinese medicines, herb of any plants belonging to the genus Epimedium is called "Yinyanghuo" irrespective of species of the plants and is infused and used as a cordial or tonic medicine. Components of this barrenwort have been studied from old and reports have been published. For example, by Akai et al. [Yakugaku Zasshi, 55, 537, 705, 719, 788 and 1139 (1935)] and Tomita et al. [Yakugaku Zasshi, 77, 114 and 212 (1957)], the substance called Icariin and the substances caled Des-O-methyl Icariin and Magnoflorine were found and the chemical structures of the respective substances have been determined. As to the phamacological characteristics, it has been reported for example by Maeda [Tokio Izi Sinsi, No. 2795, 2133 (1932)], Miyake [Okayama Igakkai Zasshi, 49, (10) 2043 (1937 )] and Hirashima et al. [Clinical Report, 4, 139 (1970)] that an extract from the barrenwort has the sperm-excitosecretory effect the hypotensive effect and the blood sugar descending effect. But their details are still unclear in many points.
We made researches on this barrenwort and succeeded in obtaining an extract having an immunostimulating activity by extracting plants belonging to the genus Epimedium. Japanese patent applications Nos. 21152/1980, 57424/1980 and 83539/1980 were filed on the basis of this finding. We further made researches to succeed in extraction and isolation of the polysaccharide PS-A, as shown in the following flow chart, having an phylactic activity and an immunostimulating activity. We have now completed the present invention based on this success. ##STR1##